Lubricating oils



Patented May 20, 1952 LUBRICATING oILs' Donald Frederick Wilcock,Marblehead, Mass,

and Murray M. Sprung, Schenectady, N. Y., assignors to General ElectricCompany, a corporation of New York No Drawing. Original applicationJanuary 16,

1947, Serial No. 722,458. Divided and this application June 20, 1951,Serial No. 232,674

8 Claims. 1

This application is a division of our earlier application Serial No.722,458, filed January 16, 1947 and assigned to the same assignee as thepresent invention.

The present invention relates to improvements in liquidorgano-substituted polysiloxanes employed for lubricating purposes. Moreparticularly the invention is concerned with a lubricating oilexhibiting improved load-bearing properties which oil comprises (1) aliquid polymeric organo-substituted polysiloxane and (2) a minorproportion, preferably a small amount, of a mixture of ingredientscomprising (a) a chlorinated saturated aliphatic monohydric alcoholester of a lower saturated aliphatic fatty acid and (b) a thioglycollicacid ester corresponding to the general formula where R. is an alkylgroup containing from 2 to 8 carbon groups.

Liquid organo-substituted polysiloxanes, for example, liquidhydrocarbon-substituted polysiloxanes, because of their outstandingresistance to heat and to oxidation at elevated temperatures, because oftheir low viscosity-temperature coefficients, and because of their lowpour points, are ideal fluids for lubrication under hydrodynamic orfluid film conditions. However, such materials when employed forlubricating purposes, under certain lubricating conditions where a fluidfilm cannot be formed or if formed has broken down, may not afiord theprotection against bearing seizure or freezing of the revolving memberor shaft supported by the bearings that has come to be expected fromcertain petroleum-base oils of like viscosity. This disparity inlubrication properties is particularly pronounced where both rubbingsurfaces are steel. This difficulty is believed due to the inability ofthe liquid polysiloxanes to maintain a continuous lubricating film onthe steel bearing surfaces when the load on the bearings has beenincreased above a certain critical point.

The primary object of this invention i to provide liquid lubricantscapable of adequately lubricating the bearing surfaces of relativelymoving metallic bodies, even under increased loads, said liquids beingcharacterized by high resistance to oxidation, little change ofviscosity with temperature, and low pour points. Other ob ects andadvantages of the present invention will become apparent from thefollowing description and claims.

2 The liquid organo substituted polysiloxanes with which this inventionis concerned are compositions comprising essentially silicon atomsconnected to one another by oxygen atoms as illustrated by the followingstructure called a siloxane structure:

wherein a preponderant number of the valences of the silicon atoms aresatisfied by the substitution thereon of organic radicals, for example,

aliphatic radicals. These compositions of matter may be prepared, e. g.,by hydrolysis of hydrolyza'ble aliphatic-substituted silanes, forinstance, 'dialiphatic dihalogenosilanes, for example, di-

' isolating the hydrolysis product and effecting reaction between thehydrolyzed product and, e. g., hexamethyl disiloxane in the presence ofsuliuric acid. More specific directions for the hydrolysis ofhydrolyzable organo-substituted silanes to form liquidorgano-substituted polysiloxanes may be found, for example, in patentsand in the literature now available in the art.

By the term "hydrolyzable organo-substituted silanes is intended to meanderivatives of'SiH4 which contain hydrolyzable groups or radicals, forexample, halogens, amino groups, alkoxy, aryloxy, and acyloxy radicals,etc., in addition to the organic groups substituted directly on thesilicon atom that are joined to the silicon through carbon-siliconlinkages. Examples of such organic radicals are aliphatic radicalsincluding alkyl radicals, for example, methyl, ethyl, propyl, isopropyl,butyl, etc.; alicyclic radicals, for example, cyclopentyl, cyclohexyl,etc.; aryl radicals, for example, phenvl, diphenyl, naphthyl, anthracyl,etc; aralkyl radicals, for example, benzvl, phenylethyl, etc. alkarylradicals, fo example, tolyl, xylyl, etc.; heterocyclic radicals, etc.;as well as hydrolyzable silanes containing two different organicradicals, for example, methyl and phenyl radicals, etc., attached to thesilicon atom. If desired, the above-mentioned radicelerated by acidicmaterials, for example, sulfuric acid, hydrochloric acid, ferricchloride, etc.,

as well as by basic materials, for example, sod um.

hydroxide, potassium hydroxide, etc. As a result of the hydrolysis andcondensation, liquid organo-substituted polysiloxanes may be producedwhich are partially or completely condensed and which may have on theaverage up to as high as three organic radicals substituted per siliconatom. The liquid organopolysiloxanes prepared in this manner consistessentially of silicon atoms joined together by oxygen atoms throughsilicon-oxygen linkages and organic radicals attached to silicon throughcarbon-silicon linkages, the remaining valences, if any, of the siliconatoms being satisfied by hydroxyl radicals and/ or byresidualunhydrolyzed radicals such as the hydrolyzable radicals listedpreviously.

Wev have now found that the frictional properties of liquidorgano-substituted polysiloxanes, especially of liquidhydrocarbon-substituted polysiloxanes containing; an average of fromabout 1.9 to 2.67, more particularly, from approximately 1.95 to 2.3hydrocarbon groups per silicon atom, may be greatly improved by in-.-corporat-ing in the said liquid polysiloxane' a minor: proportion,preferably a small amount, of a; mixture of; ingredients comprising (a)a chlorinated compound comprising a chlorinated saturated aliphaticmonohydric alcohol ester of a lowersaturated aliphatic acid and (b)acompoundcorrespondingto the generalformula This result was quitesurprising and unexpected,

gredients described under (a) and (b) above are added separately to theliquid organopolysiloxane. However, by mixing the ingredients and addingthe same to the liquid polysiloxane, a marked and, totally unpredictableincrease in the load-bearing properties of bearings lubricated with theaforementioned polysiloxanes was obtained.

Examples of chlorinated saturated aliphatic monohydric alcohol esters oflower saturated aliphatic fatty acids in which the fatty acid residuecontains from two to five, inclusive, carbon atoms, which may beemployed in the practice of our invention are chlorinated andunchlorinated saturated aliphatic monohydric alcohol esters ofchlorinated lower saturated aliphatic fatty acids, for example,monochloroethyl trichloroacetate, dichloropropyl monochlorcacetate,ethyl monochloroacetate, butyl dichloroacetate, propyl3,3,3-trichlorobutyrate, 1,3-- dichloro 2 propyltrichloroacetate, [di-(monochloromethyl) methyl trichloroacetate] butyl2,2,3-trichlorobutyrate, etc.; ated saturated aliphatic monohydricalcohol esters of unchlorinated lower saturated aliphatic fatty acids,for example, dichloroethyl acetate chlorin- V 4 (2,2-dichloroethy1acetate), 2-chloropropyl butyrate, trichloroethyl propionate(2,2,2-trichloroethyl propionate) 3,4,4,4-tetrachlorobutyl butyrate,1,3-dichloropropyl pentanoate, etc. Preferably, the chlorinatedcompounds, many examples of. which have been given above, should haveboiling points above 100 C. and should be miscible with the liquidorgano-substituted polysiloxane in the desired proportions.

Included among the various compounds corresponding to the. generalformula Where R is-an alkylgroup containing from 2 to 8 carbon atoms,which may be added to the liquid organcpolysiloxane are, for example,ethyl thiogylcollate, propyl'thioglycollate, butyl thioglycollate, hexylthioglycollate, 2-ethylbutyl thioglycollate, Z-ethylhexylthioglycollate, etc.

The amount of additives which may be'employed to effectively increasethe load-bearing properties of the liquid organopolysiloxane'lubricantsshould not be more than is necessary for the requiredpurpose, since toomuch of either the chlorinated compound or the thioglycollic acid esteradversely affects certain physical properties of the lubricant, e. g.,its flat temperatureviscosity characteristics, its pour point, lowvolatility, etc. 'We have found that, based on the weight of the liquidorgano-substituted polysiloxanes, good results are obtained'when thetotal mixture-of the chlorinated compound and the thioglycolli'cacidester comprises not more than percent, by weight, preferably fromabout 3 to I2 percent, by-weight, of the liquid organesubstitutedpolysiloxane. As regards the ratio of the Weight of the chlorinatedcompound to the thioglycollic acidester, good results are obtained ifeach of the two ingredients comprising the mixture constitutes fromapproximately topercent, by weight, based on the total weightjof themixture of the chlorinated compound and the thioglycollic acid ester. Inmany cases; opti-'- mum results are obtained when the chlorinatedcompound and the thioglycollic acid ester are present in approximatelyequal proportions, by weight.

In order that those skilledin the art may better understand how thepresent invention may be practiced, the following examples are given byway of illustration and not by way of limitation. All parts andpercentages are by weight.

A liquid methyl-substituted polysiloxane containing an average ofslightly more than two methyl groups per silicon atom was prepared byhydrolyzing substantially pure dimethyl dichlorosilane and thereaftereffecting rearrangement of the siloxane units in the hydrolyzed productwith hexamethyl disiloxane in the presence of concentrated sulfuric acidin accordance with the procedure disclosed in Patnode Patent 2,469,888,issued May 10, 1949. The viscosity of the oily liquid obtained wasapproximately 42 centistokes at about F. The load-bearing properties ofthis oily methyl polysiloxane were tested in an Almen extreme-pressurelubricant-testing machine (for a more complete description of thismachine, see Lubricants and Lubrication by James I. Clower, pages -147,published by McGraw-I-Iill' Book Co., 1939) which comprises a steelbearing split into two equal halves which are adjusted and positionedaround a rotating steel journal or shaft. The complete assembly wasimmersed in the test oil and as the steel shaft revolved (at about 600R. P. M.) the halves of the bearing were squeezed increasingly tighteraround the shaft until the pressure of the bearing on the said shaftcaused seizure of the shaft by the bearing. The average pressure inpounds per square inch exerted at the time of seizure is called theseizure bearing pressure.

In the case of the above-described liquid methyl polysiloxane containingno additives, seizure of the shaft occurred when a pressure of about 300p. s. i. was exerted by the journal on the bearing. In the followingtables are found the results of using various mixtures of chlorinatedcompounds and thioglycollic acid esters. For comparison purposes, testswere conducted (the results being shown in the same table) using each ofthe additives separately. Unless stated otherwise, the thioglycollicacid ester employed in each case was ethyl thioglycollate.

Table 1 Per Cent Added 1geizure Additive Ohln- Thimzlyi riuated colliePlessufel Com- Acid pound Ester Ethyl thioglycollate -l 5 390 Do l 103,190 2-etl1ylbutyl thioglycollate 10 605 3 Ethyl mouochloroacetate. 10l, 170 Do 5 5 13,100 Ethyl trichloroacetate. 1O 345 D0 15 730 Do. 5 512, 900 D0 5 1 5 27, 500 ClaCCOOOH(OHOl 10 1, 790(1,3-dichloro-2-propyl-trichloro- 1 The thioglycollic acid esteremployed was Z-ethylbutyl thioglyli this case, ethyl glycollate Wasemployed in place of ethyl thioglycollate.

It will, of course, be understood by those skilled in the art that otherchlorinated compounds and thioglycollic acid esters falling within ourclasses of compounds, many examples of which have been given previously,may be employed in place of the additives employed in the aboveexamples.

In addition, it will be apparent that the mixture of chlorinatedcompound and thioglycollic acid ester may be added to organo-substitutedpolysiloxanes other than the liquid methyl polysiloxane disclosed aboveto improve their lubricating properties. These include, for instance,liquid alkyl-substituted polysiloxanes, for example, liquid ethyl-,propyl-, butyl-, isopropylsubstituted polysiloxanes, etc.; liquidaryl-substituted polysiloxanes, for example, liquid phenylsubstitutedpolysiloxanes, etc.; liquid organopolysiloxanes containing differenthydrocarbons substituted on the silicon atom or atoms, for example,liquid methyl and phenyl substituted polysiloxanes, etc., as well asliquid organopolysiloxanes containing both alkyl and aryl hydrocarbonssubstituted on different silicon atoms, for example, liquidorganopolysiloxanes obtained by hydrolyzing a mixture comprisingsubstantially dimethyl dichlorosilane and diphenyl dichlorosilane andeffecting rearrangement of the siloxane units with hexamethyl disiloxanein the presence of sulfuric acid, which products are more particularlydisclosed and claimed in our 6 U. S. Patent 2,483,158 issued September27, 1949 and assigned to the same assignee as the present invention.

Our invention is particularly suitable for improving the load-bearingand frictional properties of liquid methyl polysiloxanes containing anaverage of from about 1.9 to 2.67 methyl groups per silicon atom,especially where the average ratio of methyl groups to silicon atoms isfrom about 1.95 to 2.3 methyl groups per silicon. Although, certainliquid organo-substituted polysiloxanes containing, e. g., both a phenyland a lower alkyl group, for instance, a methyl group, on the samesilicon atom have better frictional and load-bearing properties than theliquid methyl polysiloxanes, their load-bearing properties may be stillfurther improved in accordance with the teachings and disclosures of ourclaimed invention.

Still greater improvements are obtainable if liquid organo-substitutedpolysiloxanes are employed which contain chlorine atoms substituted onthe organic radical. An example of such a polysiloxane is one prepared,for example, by cohydrolyzing a mixture of chlorosilanes comprisingdimethyl dichlorosilane and a minor proportion (approximately 5 molpercent) of di- (monochlorophenyl) dichlorosilane, and thereaftereffecting rearrangement of the siloxane units with hexamethyl disiloxanein the presence of sulfuric acid.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A lubricating oil consisting essentially 01 (1) a liquid polymerichydrocarbon-substituted polysiloxane containing an average of from 1.9to 2.67 hydrocarbon groups per silicon atom, and 2) from 3 to 15 percent, by weight, based on the weight of (1) of a mixture of ingredientscomprising (a) a chlorinated saturated aliphatic monohydric alcoholester of a lower saturated aliphatic fatty acid in which the fatty acidresi-' due contains from two to five, inclusive, carbon atoms, and (b) acompound corresponding to the general formula where R. is an alkyl groupcontaining from 2 to 8 carbon atoms, the compound (b) comprising from 30to 70 per cent, by weight, of the total weight of (a) and (b).

2. A lubricating oil exhibiting good load-bearing properties whichconsists essentially of (1) a liquid polymeric hydrocarbon-substitutedpolysiloxane containing an average of from 1.9 to 2.67 hydrocarbongroups per silicon atoms, and (2) from 3 to 15 per cent, by weight,based on the weight of (1) of a mixture of ingredients comprising (a) achlorinated saturated aliphatic monohydric alcohol ester of a lowersaturated aliphatic fatty acid in which the fatty acid residue containsfrom two to five, inclusive, carbon atoms, and (b) ethyl thioglycollate,the compound (b) comprising from 30 to '70 per cent, by weight, of thetotal weight of (a) and (b).

3. A lubricating oil consisting essentially of (1) a liquidhydrocarbon-substituted polysiloxane containing an average of from about1.9 to 2.67 hydrocarbon groups per silicon atom and (2) from 3 to 12 percent, by weight, based on the weight of (1) of a mixture of ingredientscomprising (a) ethyl trichloroacetate and (b) ethyl thioglycollate,compound (1)) comprising EKBQLOQIS 7 s- $0.3"TQQ'PBEQGYIQIDTiWeightpflfjthei ifltal wweightzol: (akanditb) v 4. Alubricating oil consisting essentially oi ..(-1'):'@ a1: liquidszmethyl:polysiloxane; containing an -everageirom about 1351150123methylcgroups-per 1 i-siliconiatom sand; 12) imme- 3 I to; $12, per;cent; by weightnbased eon ztim meightiof ,1) oiiap mixturefzingredientsgcomprising I la) a ethyl .trichloroaca etaltei'a'nd :ib)ethykthioglycollate, compound l-(b) --:comprising -fromv3mto 70 per.vcent,- by weight of --ithe=tota1weightaof 1(a); and? lb) A *lu-bricatingoil; :consisting 1 essentially of (1) :i-arli-quid methyl. polysiloxane;containing an iaayerage ofvfrom, aboutl95 Ito 2.3 methyl groupsgpenisilicon atom and 1(2 )efrom 3 toilzhpencent by -:x veight basedon-. the weight-10f (1):.v oiv a-mixture of 1 ingredients :1-comp-rising :(a) l,3-. dichlor0 e2- -;:-propylertrichloroacetate and--.(b) ethyl .thioglycollate, the compound (1)) comprisingfrom-fiO-to (lpeit. cent, by Weight, oflthei-total weight-of; (a)

aandetb) t .(LzA I; lubricating 1 011 ,-:consisting essentially ",of(.1):-:a liquid i'methyl*polysiloxane containing from about 1.95 to.-2.3 methyl groups 'per: silicon atom -.and (2): from-3:130 12 percent, by weight, based on the 'weightof .(l)-of a mixture of ingredientsh comprising (a) butyl 2,2,3-trichlorobutyrate, and --1(b)e ethylthioglycollate; the compound (1)) com- -prising fromBO to 70per cent,-by--weight, of. the

' "-7clAalubricating toil consisting essentially-10f (-1) ;-':--aliquid; methyl; polysiloxane :containing .-;from about 1295 to: 2.3-methyl igroups per siliconatom i -and :(2) :from31 to 12 per cent, byWeight, based 'i; on:the-we ight of ('1).'of= a mixture vof ingredientsqcomprising' (a) ethyl-monochloroacetate and 4b) ethyl thicglycollatel;the' compound b):-co1 nprisi: ing from 301:0 7Qpe1acent;bylweight,ofihe-total a-wei'ght of '(a) and (19) '8.:A'1ubricating oilconsistingl'essentially of (1) e, iliquidw methyl polysiloxanecontaining from about 1.95 to 2.3;methylfgroups per silicon atom and"(2) I from 3.-1to. 12. per cent, by- Weight, based eon the weight of.(1); 'of a' mixture of ingredients comprising (a) ethyltrichloroacetatei and b1 2- ethylbutyllthioglycollate,r the vcompound.(b) com- ;prising from 30 .to Wiper centpby-weight, oietheitotalweightof (a). and (b), V

,DONALD: FREDERICK WILCOCK.

MURRAY M. SPRUNG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,384,384 McGregor .r Sept. 4,1945 2,523,535 Merker Nov. 7-, 1950

1. A LUBRICATING OIL CONSISTING ESSENTIALLY OF (1) A LIQUID POLYMERICHYDROCARBON-SUBSTITUTED POLYSILOXANE CONTAINING AN AVERAGE OF FROM 1.9TO 2.67 HYDROCARBON GROUPS PER SILICONE ATOM, AND (2) FROM 3 TO 15 PERCENT, BY WEIGHT, BASED ON THE WEIGHT OF (1) OF A MIXTURE OF INGREDIENTSCOMPRISING (A) A CHLORINATED SATURATED ALIPHATIC MONOHYDRIC ALCOHOLESTER OF A LOWER SATURATED ALIPHATIC FATTY ACID IN WHICH THE FATTY ACIDRESIDUE CONTAINS FROM TWO TO FIVE, INCLUSIVE, CARBON ATOMS, AND (B) ACOMPOUND CORRESPONDING TO THE GENERAL FORMULA